Body Fat Calculator
This calculator is for informational purposes only and is not a substitute for professional medical advice. Consult a healthcare provider for personal health decisions.
US Navy method using neck, waist, and hip measurements
How Body Fat Percentage Is Estimated
Body fat percentage measures what fraction of your total weight is adipose tissue versus lean mass (muscle, bone, organs, water). The U.S. Navy method estimates it from simple circumference measurements and height, validated against underwater weighing with reasonable accuracy for most adults. For men: body fat % = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. For women, hip circumference is added: body fat % = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height)) − 450. All measurements are in centimeters (or inches consistently).
Example for a man 180 cm tall with neck 38 cm and waist 85 cm. Waist minus neck = 47 cm. log₁₀(47) ≈ 1.672. log₁₀(180) ≈ 2.255. Plug in: 495 ÷ (1.0324 − 0.19077 × 1.672 + 0.15456 × 2.255) − 450 = 495 ÷ 1.062 − 450 ≈ 16.1% body fat. For reference, fit men often fall in the 10–20% range, average men 18–24%, and fit women 18–28% with average women 25–31%. Essential fat minimums are roughly 2–5% for men and 10–13% for women.
Measure consistently for reliable tracking: neck just below the larynx, waist at the navel level after a normal exhale, hips at the widest point for women. Use a flexible tape measure, keep it level, and avoid pulling tight. Take each measurement twice and average. Small technique errors can shift results by 1–2 percentage points, so focus on trends over weeks rather than obsessing over a single reading.
The Navy method is convenient and free but less precise than DEXA scans, hydrostatic weighing, or professional caliper testing by a skilled technician. It can underestimate fat in very lean individuals and overestimate it in those with large waist measurements from visceral fat or bloating. Pair the number with how clothes fit, strength performance, and waist-to-height ratio for a fuller picture.
This calculator applies the Navy equations to your measurements and classifies the result into standard fitness categories. Re-measure monthly under the same conditions to track progress during a fat-loss or muscle-building program without expensive lab equipment.
Examples
| Example | Result |
|---|---|
| Male 180 cm, neck 38 cm, waist 85 cm | Body fat ~16.1% |
| Male 175 cm, neck 37 cm, waist 78 cm | Body fat ~12.0% |
| Female 165 cm, neck 32 cm, waist 70 cm, hip 95 cm | Body fat ~24.9% |
| Male 190 cm, neck 40 cm, waist 92 cm | Body fat ~18.2% |
| Female 160 cm, neck 30 cm, waist 65 cm, hip 90 cm | Body fat ~21.9% |
| Male 170 cm, neck 36 cm, waist 95 cm | Body fat ~26.3% |
| Female 170 cm, neck 33 cm, waist 75 cm, hip 100 cm | Body fat ~28.1% |
Frequently asked questions
For men, 10–20% is generally fit; 18–24% is average. For women, 18–28% is fit; 25–31% is average. Essential fat minimums are about 2–5% (men) and 10–13% (women).
Measure at the navel level after a normal exhale, standing relaxed. Keep the tape horizontal and snug but not compressing skin.
It typically agrees with lab methods within 3–4 percentage points for most people. Consistent self-measurement over time matters more than absolute precision.